o_stream_send_istream(): Get input stream size with i_stream_get_size() instead of _stat().
o_stream_send_istream(): Get input stream size with i_stream_get_size() instead of _stat().

jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch